I had planned to have a bit more verticality in the level, but I had a hard time trying to get the Navmesh to only go where I wanted it to, so I have to give it custom geometry and tweak the settings to barely get it to only go in the main area. Had I had more time, I would I've built a tool to manually author the Navmesh, so I could generate the basic one, and remove anywhere I didn't wanted the mice to go.
Thank you for playing the game and leaving a nice comment!